xfs: convert open-coded xfs_rtword_t pointer accesses to helper

There are a bunch of places where we use open-coded logic to find a
pointer to an xfs_rtword_t within a rt bitmap buffer.  Convert all that
to helper functions for better type safety.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_rtbitmap.c

@@ -103,7 +103,6 @@ xfs_rtfind_back(
 	int		bit;		/* bit number in the word */
 	xfs_fileoff_t	block;		/* bitmap block number */
 	struct xfs_buf	*bp;		/* buf for the block */
-	xfs_rtword_t	*bufp;		/* starting word in buffer */
 	int		error;		/* error value */
 	xfs_rtxnum_t	firstbit;	/* first useful bit in the word */
 	xfs_rtxnum_t	i;		/* current bit number rel. to start */
@@ -121,12 +120,12 @@ xfs_rtfind_back(
 	if (error) {
 		return error;
 	}
-	bufp = bp->b_addr;
+
 	/*
 	 * Get the first word's index & point to it.
 	 */
 	word = xfs_rtx_to_rbmword(mp, start);
-	b = &bufp[word];
+	b = xfs_rbmblock_wordptr(bp, word);
 	bit = (int)(start & (XFS_NBWORD - 1));
 	len = start - limit + 1;
 	/*
@@ -173,9 +172,9 @@ xfs_rtfind_back(
 			if (error) {
 				return error;
 			}
-			bufp = bp->b_addr;
+
 			word = mp->m_blockwsize - 1;
-			b = &bufp[word];
+			b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the previous word in the buffer.
@@ -219,9 +218,9 @@ xfs_rtfind_back(
 			if (error) {
 				return error;
 			}
-			bufp = bp->b_addr;
+
 			word = mp->m_blockwsize - 1;
-			b = &bufp[word];
+			b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the previous word in the buffer.
@@ -278,7 +277,6 @@ xfs_rtfind_forw(
 	int		bit;		/* bit number in the word */
 	xfs_fileoff_t	block;		/* bitmap block number */
 	struct xfs_buf	*bp;		/* buf for the block */
-	xfs_rtword_t	*bufp;		/* starting word in buffer */
 	int		error;		/* error value */
 	xfs_rtxnum_t	i;		/* current bit number rel. to start */
 	xfs_rtxnum_t	lastbit;	/* last useful bit in the word */
@@ -296,12 +294,12 @@ xfs_rtfind_forw(
 	if (error) {
 		return error;
 	}
-	bufp = bp->b_addr;
+
 	/*
 	 * Get the first word's index & point to it.
 	 */
 	word = xfs_rtx_to_rbmword(mp, start);
-	b = &bufp[word];
+	b = xfs_rbmblock_wordptr(bp, word);
 	bit = (int)(start & (XFS_NBWORD - 1));
 	len = limit - start + 1;
 	/*
@@ -347,8 +345,9 @@ xfs_rtfind_forw(
 			if (error) {
 				return error;
 			}
-			b = bufp = bp->b_addr;
+
 			word = 0;
+			b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the previous word in the buffer.
@@ -392,8 +391,9 @@ xfs_rtfind_forw(
 			if (error) {
 				return error;
 			}
-			b = bufp = bp->b_addr;
+
 			word = 0;
+			b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the next word in the buffer.
@@ -541,7 +541,6 @@ xfs_rtmodify_range(
 	int		bit;		/* bit number in the word */
 	xfs_fileoff_t	block;		/* bitmap block number */
 	struct xfs_buf	*bp;		/* buf for the block */
-	xfs_rtword_t	*bufp;		/* starting word in buffer */
 	int		error;		/* error value */
 	xfs_rtword_t	*first;		/* first used word in the buffer */
 	int		i;		/* current bit number rel. to start */
@@ -560,12 +559,12 @@ xfs_rtmodify_range(
 	if (error) {
 		return error;
 	}
-	bufp = bp->b_addr;
+
 	/*
 	 * Compute the starting word's address, and starting bit.
 	 */
 	word = xfs_rtx_to_rbmword(mp, start);
-	first = b = &bufp[word];
+	first = b = xfs_rbmblock_wordptr(bp, word);
 	bit = (int)(start & (XFS_NBWORD - 1));
 	/*
 	 * 0 (allocated) => all zeroes; 1 (free) => all ones.
@@ -599,14 +598,15 @@ xfs_rtmodify_range(
 			 * Get the next one.
 			 */
 			xfs_trans_log_buf(tp, bp,
-				(uint)((char *)first - (char *)bufp),
-				(uint)((char *)b - (char *)bufp));
+				(uint)((char *)first - (char *)bp->b_addr),
+				(uint)((char *)b - (char *)bp->b_addr));
 			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
 			if (error) {
 				return error;
 			}
-			first = b = bufp = bp->b_addr;
+
 			word = 0;
+			first = b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the next word in the buffer
@@ -639,14 +639,15 @@ xfs_rtmodify_range(
 			 * Get the next one.
 			 */
 			xfs_trans_log_buf(tp, bp,
-				(uint)((char *)first - (char *)bufp),
-				(uint)((char *)b - (char *)bufp));
+				(uint)((char *)first - (char *)bp->b_addr),
+				(uint)((char *)b - (char *)bp->b_addr));
 			error = xfs_rtbuf_get(mp, tp, ++block, 0, &bp);
 			if (error) {
 				return error;
 			}
-			first = b = bufp = bp->b_addr;
+
 			word = 0;
+			first = b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the next word in the buffer
@@ -676,8 +677,9 @@ xfs_rtmodify_range(
 	 * Log any remaining changed bytes.
 	 */
 	if (b > first)
-		xfs_trans_log_buf(tp, bp, (uint)((char *)first - (char *)bufp),
-			(uint)((char *)b - (char *)bufp - 1));
+		xfs_trans_log_buf(tp, bp,
+			(uint)((char *)first - (char *)bp->b_addr),
+			(uint)((char *)b - (char *)bp->b_addr - 1));
 	return 0;
 }
 
@@ -775,7 +777,6 @@ xfs_rtcheck_range(
 	int		bit;		/* bit number in the word */
 	xfs_fileoff_t	block;		/* bitmap block number */
 	struct xfs_buf	*bp;		/* buf for the block */
-	xfs_rtword_t	*bufp;		/* starting word in buffer */
 	int		error;		/* error value */
 	xfs_rtxnum_t	i;		/* current bit number rel. to start */
 	xfs_rtxnum_t	lastbit;	/* last useful bit in word */
@@ -794,12 +795,12 @@ xfs_rtcheck_range(
 	if (error) {
 		return error;
 	}
-	bufp = bp->b_addr;
+
 	/*
 	 * Compute the starting word's address, and starting bit.
 	 */
 	word = xfs_rtx_to_rbmword(mp, start);
-	b = &bufp[word];
+	b = xfs_rbmblock_wordptr(bp, word);
 	bit = (int)(start & (XFS_NBWORD - 1));
 	/*
 	 * 0 (allocated) => all zero's; 1 (free) => all one's.
@@ -845,8 +846,9 @@ xfs_rtcheck_range(
 			if (error) {
 				return error;
 			}
-			b = bufp = bp->b_addr;
+
 			word = 0;
+			b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the next word in the buffer.
@@ -891,8 +893,9 @@ xfs_rtcheck_range(
 			if (error) {
 				return error;
 			}
-			b = bufp = bp->b_addr;
+
 			word = 0;
+			b = xfs_rbmblock_wordptr(bp, word);
 		} else {
 			/*
 			 * Go on to the next word in the buffer.

fs/xfs/libxfs/xfs_rtbitmap.h

@@ -158,6 +158,17 @@ xfs_rbmblock_to_rtx(
 	return rbmoff << mp->m_blkbit_log;
 }
 
+/* Return a pointer to a bitmap word within a rt bitmap block. */
+static inline xfs_rtword_t *
+xfs_rbmblock_wordptr(
+	struct xfs_buf		*bp,
+	unsigned int		index)
+{
+	xfs_rtword_t		*words = bp->b_addr;
+
+	return words + index;
+}
+
 /*
  * Functions for walking free space rtextents in the realtime bitmap.
  */